Memory mapping is the translation between the logical address space and the physical memory. The objectives of memory mapping are (1) to translate from logical to physical address, (2) to aid in memory protection (q.v.), and (3) to enable better management of memory resources. Mapping is important to computer performance, both locally (how long it takes to execute an instruction) and globally (how long it takes to run a set of programs). In effect, each time a program presents a logical memory address and requests that the corresponding memory word be accessed, the mapping mechanism must translate that address into an appropriate physical memory location. The simpler this translation, the lower the implementation cost and the higher the performance of the individual memory reference.

Definition: Flash memory (Known as Flash Storage) is a type of non-volatile storage memory that can be written or programmed in units called “Sector” or a “Block.” Flash Memory is EEPROM (Electronically Erasable Programmable Read-Only Memory) means that it can retain its contents when the power supply removed, but whose contents can be quickly erased and rewritten at the byte level by applying a short pulse of higher voltage. This is called flash erasure, hence the name. Flash memory is currently both too expensive and too slow to serve as main memory.

Optical Mark Recognition (OMR) is the technology of electronically extracting intended data from marked fields, such as checkboxes and fill-in fields, on printed forms. It is generally distinguished from OCR by the fact that a recognition engine is not required. This requires the image to have high contrast and an easily-recognizable or irrelevant shape.

OCRstands for optical character recognition, a wonderful and marvellous technology. It enables you to convert previously printed text material into information your computer can understand, without having to retype it. Have you ever had a story or an article or a magazine clipping that you wanted to have in your computer, but the thought of retyping the entire thing was overwhelming? Or just boring? That's what OCR is for.

Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles or domains, each storing one bit of data. Andrew Bobeck invented the Bubble Memory in 1970. His development of the magnetic core memory and the development of the twistor memory put him in a good position for the development of Bubble Memory.

Entity Integrity: - No attribute participating in the primary key of a base relation allowed containing any nulls. Primary key performs the unique identification function in a relational model. Thus a null primary key value within a base relation would be like saying that there was some entity that had no known identity. An entity that cannot be identified is a contradiction in terms, hence the name entity integrity.

DDRAM: - Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle (the rising and falling edges), effectively doubling the memory chip's data throughput. DDR-SDRAM also consumes less power, which makes it well suited to notebook computers. DDR-SDRAM is also called SDRAM II And DDRAM.

Hard Disk Access time is the total elapsed time between the initiation of a particular request for data and receipt of the first bit of that data.

Direct access devices (Hard Disk Drive) require varying times to position a disk head over a particular record. In the case of a moving-head disk drive, this involves positioning the comb (head assembly, as in Fig.) to the designated cylinder, plus rotation of the selected track to the desired record. Comb-movement times for a typical medium-sized disk drive are shown in Fig.

Definition: EPROM (pronounced ee-prom) stands for Erasable Programmable Read-Only Memory. EPROM is a type of ROM chip that can retain the data even if there is no power supply. The data can be erased and reprogrammed by using ultraviolet (UV) light. The UV light clears the data on the chip so that it can reprogram. For writing and erasing data on the EPROM, we need a particular device which is known as PROM programmer. The process of programming an EPROM is often called BURNING, and the box into which it is plugged to program it an EPROM burner.

Definition of parity memory: Some Random Access Memory (RAM) chips have built-in error-checking functions that use a process called parity. Chips that use parity have an extra bit for every eight bits of data. In the parity process, as the eight bits receive binary data (data represented by 1s and 0s), the chip adds all the 1s, and if that total is odd, the extra bit is set to 1.The most common data error-checking and validation technique is the Vertical Redundancy Check (VRC) often called a parity check.